The present invention relates to apparatus for guiding a moving web in tension and, more particularly, to apparatus to be used in spaced combinations of two or more for supporting a roll on a shaft and providing a signal output reflecting force on the roll at the points of support comprising, a collar non-movingly attached to the shaft; a pair of resiliently bendable opposed beams carried by the collar and extending therefrom parallel to opposite sides of the shaft; a cylindrical support member disposed over the shaft and carried by the pair of beams, the support member having an axial bore for the shaft to pass through which is a clearance fit to the shaft; a ball bearing fit onto the outer periphery of the support member and having an outer diameter sized to have the roll slid thereover to be supported for rotation thereby; and, a plurality of strain gauges disposed on the upper and lower surfaces of respective ones of the pair of beams to provide signals at outputs thereof indicating the strain in each of the strain gauges.
Tension transducers are well known in the art and are manufactured and sold commercially by a number of companies including the applicant's company, Dover Flexo Electronics, Inc. A web tension transducer is used to measure tension in any moving web. The output signal produced can be displayed for manual control of the tension or can be used for automated control. They are typically used in printing presses, coaters, laminators, textile machines, slitter-rewinders, sheeters, paper-making machines, and any other machines which in some way processes a continuous web of paper, plastic film, metal, textile, non-woven textile, felt, rubber, or any combination of the foregoing. Variations of web tension can cause web breakage, slack web, wrinkling, curling, stretching, and in general, poor quality product and excessive waste. These problems can be eliminated by proper control of web tension. The basis of proper control is tension measurement. The basis of measurement is a transducer which will convert a force (web tension) into an electrical signal which can be used for control purposes. The transducer must be accurate regardless of web speed and tension or it will not allow the correction of the aforementioned problems.
Tension transducers can be placed into two general classifications. In one instance, as typified by co-pending application Ser. No. 870,113, filed June 3, 1986 (U.S. Pat. No. 4,691,579) by applicant herein entitled TENSION TRANSDUCER and assigned to the assignee of this invention, the transducer is incorporated into a supportive joint used to support a rotating or non-rotating shaft having the roll over which the web is moving mounted thereof. The joints are used in pairs on the outside of the roll.
A prior art approach to the second general classification as wherein the present invention is applicable is shown in FIGS. 1 and 2. In this case, the transducer is incorporated within the roll instead of being on the outside as part of a supportive joint. In the prior art idler roll/transducer 10 of FIGS. 1 and 2, there is a hollow mounting flange 12 by which the roller/transducer 10 can be mounted to a side surface (not shown) of the apparatus into which it is incorporated. A first steel shaft 14 extends outward rigidly and perpendicularly to the flange 12. An elongated, cylindrical, aluminum beam member is concentrically attached to the end of the shaft 14 as with allen screws 18 passing from inside the flange 12 through bores (not shown) in the steel shaft 14 into threaded engagement with the beam member 16. A second steel shaft 20 is concentrically fit into the other end of the beam member 16 and extends rigidly outward therefrom. The two ends of the beam member 16 at 22 are cylindrical and have a bearing 24 press-fit thereon. Each end 22 has a bore 26 therethrough through which the shafts 14, 20 pass, respectively. The bores 26 are a close-clearance fit to the shafts 14, 20 to allow for deflection movement. Adjacent each end, a pair of opposed beams 28 are formed into the beam member 16. A cylindrical stainless steel roll 30 is fit over the bearings 24 to roll thereon. The web in which the tension is to be controlled passes over the roll 30 and the roll/transducer 10 is positioned so that the force of the web is in the direction of the arrows 32. A pair of strain gauges 34 are disposed on the upper and lower surfaces of the inward beams 28 with respect to the direction of applied force. The force of the web against the roll 30 applies a force through the bearings 24 against the beam ends 22 causing them to deflect the beams 28 and impart a strain into the strain gauges 34 which, in turn, produce an electrical signal which can be used for control.
As can be appreciated from a review of the prior art apparatus of FIGS. 1 and 2, there is a high potential for non-linearity and part failure because of the use of dissimilar metals and the composite construction of the central member comprising the steel shafts 14, 20 and aluminum beam member 16. The amount of deflection movement being measured is so small that any minor misalignment, free play, or failure in one or both of the joints between the shafts 14, 20 and the beam member can cause catastrophic failure and/or inaccuracies in the use of the prior art roll/transducer 10.
As can also be appreciated, the above-described construction does not lend itself to a wide variety of sizes of easy manufacture. To produce a different width of roll 30, a corresponding beam member 16 of like size must be constructed as well. As can be seen and appreciated, the beam member 16 is of complex construction and not quickly and economically manufacturable in a new length.
Wherefore, it is the object of the present invention to provide a combined roll/transducer for web support and tension measurement which is easily manufactured in varying widths.
It is another object of the present invention to provide a web tension roll/transducer where the transducers are located within the roll but wherein a through shaft of unitary construction is employed.
Other objects and benefits of the present invention will become apparent from the description contained hereinafter taken in conjunction with the drawing figures which accompany it.